You can only have 1 copy of your investigator's signature card in your deck. These cards have no level, which is different from having level 0, and the deckbuilding rules only allow you to add cards of level 0-5 to your main deck. (Note: Signature cards in the Core Set were accidentally misprinted using the same template as level 0 cards. Starting with The Dunwich Legacy deluxe, signature cards will be printed as cards with no level (e.g. Zoey's Cross).

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